/**
 * Copyright (C) 2016-2016  Hover Winter<hoverwinter@gmail.com>.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.cherrypt.api.common.util;

/**
 * RFC1738 URLEncoder
 */
public class URLEncoder {
    private URLEncoder() {
    }

    private static final String[] hex = {
            "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07",
            "%08", "%09", "%0A", "%0B", "%0C", "%0D", "%0E", "%0F",
            "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17",
            "%18", "%19", "%1A", "%1B", "%1C", "%1D", "%1E", "%1F",
            "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27",
            "%28", "%29", "%2A", "%2B", "%2C", "%2D", "%2E", "%2F",
            "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37",
            "%38", "%39", "%3A", "%3B", "%3C", "%3D", "%3E", "%3F",
            "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47",
            "%48", "%49", "%4A", "%4B", "%4C", "%4D", "%4E", "%4F",
            "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57",
            "%58", "%59", "%5A", "%5B", "%5C", "%5D", "%5E", "%5F",
            "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67",
            "%68", "%69", "%6A", "%6B", "%6C", "%6D", "%6E", "%6F",
            "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77",
            "%78", "%79", "%7A", "%7B", "%7C", "%7D", "%7E", "%7F",
            "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87",
            "%88", "%89", "%8A", "%8B", "%8C", "%8D", "%8E", "%8F",
            "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97",
            "%98", "%99", "%9A", "%9B", "%9C", "%9D", "%9E", "%9F",
            "%A0", "%A1", "%A2", "%A3", "%A4", "%A5", "%A6", "%A7",
            "%A8", "%A9", "%AA", "%AB", "%AC", "%AD", "%AE", "%AF",
            "%B0", "%B1", "%B2", "%B3", "%B4", "%B5", "%B6", "%B7",
            "%B8", "%B9", "%BA", "%BB", "%BC", "%BD", "%BE", "%BF",
            "%C0", "%C1", "%C2", "%C3", "%C4", "%C5", "%C6", "%C7",
            "%C8", "%C9", "%CA", "%CB", "%CC", "%CD", "%CE", "%CF",
            "%D0", "%D1", "%D2", "%D3", "%D4", "%D5", "%D6", "%D7",
            "%D8", "%D9", "%DA", "%DB", "%DC", "%DD", "%DE", "%DF",
            "%E0", "%E1", "%E2", "%E3", "%E4", "%E5", "%E6", "%E7",
            "%E8", "%E9", "%EA", "%EB", "%EC", "%ED", "%EE", "%EF",
            "%F0", "%F1", "%F2", "%F3", "%F4", "%F5", "%F6", "%F7",
            "%F8", "%F9", "%FA", "%FB", "%FC", "%FD", "%FE", "%FF"
    };

    /**
     * Encode a string according to RFC 1738.
     * <p/>
     * <quote> "...Only alphanumerics [0-9a-zA-Z], the special characters "$-_.+!*'()," [not
     * including the quotes - ed], and reserved characters used for their reserved purposes
     * may be used unencoded within a URL."</quote>
     * <p/>
     * <ul> <li><p>The ASCII characters 'a' through 'z', 'A' through 'Z', and '0' through
     * '9' remain the same.
     * <p/>
     * <li><p>The unreserved characters - _ . ! ~ * ' ( ) remain the same.
     * <p/>
     * <li><p>All other ASCII characters are converted into the 3-character string "%xy",
     * where xy is the two-digit hexadecimal representation of the character code
     * <p/>
     * <li><p>All non-ASCII characters are encoded in two steps: first to a sequence of 2 or
     * 3 bytes, using the UTF-8 algorithm; secondly each of these bytes is encoded as "%xx".
     * </ul>
     *
     * @param s The string to be encoded
     * @return The encoded string
     */
    public static String encodeUTF8(final String s) {
        final StringBuffer sbuf = new StringBuffer();
        final char[] sChars = s.toCharArray();
        final int len = sChars.length;
        for (int i = 0; i < len; i++) {
            final int ch = sChars[i];
            if ('A' <= ch && ch <= 'Z') {   // 'A'..'Z'
                sbuf.append((char) ch);
            } else if ('a' <= ch && ch <= 'z') { // 'a'..'z'
                sbuf.append((char) ch);
            } else if ('0' <= ch && ch <= '9') { // '0'..'9'
                sbuf.append((char) ch);
            } else if (ch == '-' || ch == '_'   // unreserved
                    || ch == '.' || ch == '!'
                    || ch == '~' || ch == '*'
                    || ch == '\'' || ch == '('
                    || ch == ')') {
                sbuf.append((char) ch);
            } else if (ch <= 0x007f) {   // other ASCII
                sbuf.append(hex[ch]);
            } else if (ch <= 0x07FF) {   // non-ASCII <= 0x7FF
                sbuf.append(hex[0xc0 | (ch >> 6)]);
                sbuf.append(hex[0x80 | (ch & 0x3F)]);
            } else {         // 0x7FF < ch <= 0xFFFF
                sbuf.append(hex[0xe0 | (ch >> 12)]);
                sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]);
                sbuf.append(hex[0x80 | (ch & 0x3F)]);
            }
        }
        return sbuf.toString();
    }

    public static String encodeBytes(final byte[] s) {
        final StringBuffer sbuf = new StringBuffer();
        final int len = s.length;
        for (int i = 0; i < len; i++) {
            final int ch = (s[i] & 0xff);
            if ('A' <= ch && ch <= 'Z') {   // 'A'..'Z'
                sbuf.append((char) ch);
            } else if ('a' <= ch && ch <= 'z') { // 'a'..'z'
                sbuf.append((char) ch);
            } else if ('0' <= ch && ch <= '9') { // '0'..'9'
                sbuf.append((char) ch);
            } else if (ch == '-' || ch == '_'   // unreserved
                    || ch == '.' || ch == '!'
                    || ch == '~' || ch == '*'
                    || ch == '\'' || ch == '('
                    || ch == ')') {
                sbuf.append((char) ch);
            } else {   // other ASCII
                sbuf.append(hex[ch]);
            }
        }
        return sbuf.toString();
    }

}
